1. Field of the Invention
The present invention relates to a control device of an internal combustion engine including a first fuel injection unit (an injector for in-cylinder injection) injecting fuel into a cylinder and a second fuel injection unit (an injector for intake manifold injection) for injecting the fuel into an intake manifold or an intake port, and particularly to a control device for executing purge processing of vaporized fuel gas.
2. Description of the Background Art
A certain kind of known internal combustion engine includes an intake manifold injector for injecting fuel into an intake manifold of an engine and an in-cylinder injector for always injecting the fuel into a combustion chamber of the engine, and is configured such that the intake manifold injector stops the fuel injection when an engine load is lower than a predetermined set load, and injects the fuel when the engine load is higher than the set load. In this internal combustion engine, a total injection amount, which is a sum of amounts of the fuel injected from both injectors, is predetermined as a function of the engine load, and increases with the engine load.
Japanese Patent Laying-Open No. 2001-020837 has disclosed an internal combustion engine of a dual injection type, which includes in-cylinder injectors for injecting fuel into cylinders and intake manifold injectors injecting the fuel into an intake manifold or intake ports. In this structure, these injectors are selectively used according to an operation state of the engine for achieving, e.g., stratified charge combustion in a low load operation region and homogenous combustion in a high load operation region, and for achieving the fuel injection with a predetermined sharing ratio according to the operation state. Thereby, fuel consumption characteristics and output characteristics are improved.
Japanese Patent Laying-Open No. 05-231221 has disclosed an internal combustion engine of a fuel injection type for preventing fluctuations in engine output torque at the times of start and stop of fuel injection by an intake manifold injector of the above kind of internal combustion engine. This fuel injection internal combustion engine includes first fuel injection valves for injecting fuel into an engine intake manifold, and second fuel injection valves for injecting the fuel into engine combustion chambers, and is configured to stop the fuel injection from the first fuel injection valves when an operation state of the engine is in a predetermined operation region, and to inject the fuel from the first fuel injection valves when the operation state of the engine is outside the above predetermined operation region. This internal combustion engine includes a unit, which estimates an amount of fuel adhering to an inner wall surface of the intake manifold when the first fuel injection valve starts the fuel injection, and estimates an amount of adhered fuel flowing into the combustion chamber of the engine when the first fuel injection valve stops the fuel injection. When the first fuel injection valve starts the fuel injection, the amount of fuel to be injected from the second fuel injection valve is corrected and increased by the above amount of the adhesion fuel. When the first fuel injection valve stops the fuel injection, the amount to be injected from the second fuel injection valve is corrected and decreased by the above amount of inflow fuel.
According to the fuel injection internal combustion engine, when the first fuel injection valve starts the fuel injection, the amount of fuel to be injected from the second fuel injection valve is corrected and increased by the amount of the adhesion fuel. Thereby, the amount of fuel practically supplied to the combustion chamber of the engine is equal to a required fuel amount. When the first fuel injection valve stops the fuel injection, the amount to be injected from the second fuel injection valve is corrected and decreased by the inflow amount. Thereby, the amount of fuel practically supplied into the engine combustion chamber is equal to the required fuel amount. As a result, it is possible to prevent fluctuations in engine output torque at the time of start and stop of the fuel injection from the first fuel injection valve.
Generally, in a vehicle with an internal combustion engine, a collection device such as a canister temporarily absorbs fuel vapor produced in a fuel tank or the like, and the fuel vapor absorbed by the collection device such as canister or the like is purged and introduced into an intake system of the internal combustion engine according to an operation state of the internal combustion engine so that the fuel vapor is prevented from dispersing into an atmosphere.
As described above, when the purge processing is executed for purging the fuel vapor and introducing it into the intake system of the internal combustion engine, the purged fuel, of which amount depends on a concentration of the purged fuel vapor (i.e., a so-called purge gas concentration) and its flow rate, is introduced into the engine in addition to the fuel injected from the injector. This may cause fluctuations in air-fuel ratio to fluctuate and impair the combustion. For executing such purge processing, it is required to correct the fuel injection amount and the purged fuel amount for avoiding problems, i.e., lowering of the internal combustion engine performance and deterioration of emissions.
Japanese Patent Laying-Open No. 2002-081351 has disclosed a control device of an engine, which allows the purge of a large amount of fuel within a range not deteriorating drivability and independently of fluctuations in characteristics of each engine, and prevents releasing of vaporized fuel into an atmosphere, which may be caused when exceeding an absorption limit of a canister. This control device of the engine is configured to perform the purge by controlling a degree of opening of a purge control valve, which is arranged at a purge pipe connecting an intake manifold and a fuel tank, and includes a determining unit determining stability of a combustion state of the engine, and a control unit performing purge control to increase a purge amount when the determining unit determines that the stability of the combustion state is high, and to decrease the purge amount when the determining unit determines that the stability of the combustion is low.
This engine control device controls the purge amount based on the stability of the combustion state of the engine. Therefore, the purge of a large amount of fuel can be performed within a range not deteriorating the high drivability, independently of fluctuations in the engine, and it is possible to prevent reliably the release of the vaporized fuel due to exceeding of the absorption limit of the canister.
However, Japanese Patent Laying-Open Nos. 2001-020837 and 05-231221 have not disclosed correction of the fuel injection amount during execution of the purge processing. Therefore, the internal combustion engines of the fuel injection type disclosed in these publications cannot overcome the problems (e.g., lowering of performance due to adhesion of deposits and emission deterioration due to fluctuations in air-fuel ratio) during execution of the purge processing, although these engines can prevent fluctuations in engine output torque at the start and stop of fuel injection from the first fuel injection valve.
Further, the engine disclosed in the above Japanese Patent Laying-Open No. 2002-081351 does not have a first fuel injection unit injecting fuel into a cylinder and a second fuel injection unit injecting the fuel into an intake manifold, and it is difficult to apply this structure to the internal combustion engine having two fuel injection units (injectors).